<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 
        
            可以三个正方形

            按照相同的角色，旋转
            就出来了
        */


        .box {
            background: red;
            width: 80px;
            height: 80px;
            position: relative;
            text-align: center;
        }

        .box:before,
        .box:after {
            content: "";
            position: absolute;
            top: 0;
            left: 0;
            height: 80px;
            width: 80px;
            background: red;
        }

        .box:before {
            -webkit-transform: rotate(30deg);
            -moz-transform: rotate(30deg);
            -ms-transform: rotate(30deg);
            -o-transform: rotate(30deg);
        }

        .box:after {
            -webkit-transform: rotate(60deg);
            -moz-transform: rotate(60deg);
            -ms-transform: rotate(60deg);
            -o-transform: rotate(60deg);
        }
    </style>
</head>

<body>
    <div class="box"></div>
</body>

</html>